How do we ensure that IR beams in IR proximity sensors reflect directly back to the sensor?

Question

I know in a proximity sensor an infrared beam is sent out and it is reflected back to a sensor where it does time calculations. Given the laws of reflection, I would’ve guessed that the IR beam would just reflect in random directions upon hitting anything other than a flat surface perpendicular to the proximity sensor. How is this issue resolved?

Tagging this physics but it could easily be engineering

In: 3

Answer 1

You can split up a reflection in two main types Specular reflection and Diffuse reflection,

Specular reflection is like a mirror all light incoming from one direction is reflected out in another single direction. Diffuse reflection is when light is reflected from a surface in multiple directions like a painted white wall.

So unless you have a perfect mirror with only Specular reflection some will be reflected back to the sensor.

I would assume that IR proximity sensors have limitations in material and will have problems working with a mirror but other materials will reflect enough light back to the sensor.

Answer 2

You can split up a reflection in two main types Specular reflection and Diffuse reflection,

Specular reflection is like a mirror all light incoming from one direction is reflected out in another single direction. Diffuse reflection is when light is reflected from a surface in multiple directions like a painted white wall.

So unless you have a perfect mirror with only Specular reflection some will be reflected back to the sensor.

I would assume that IR proximity sensors have limitations in material and will have problems working with a mirror but other materials will reflect enough light back to the sensor.